Recording material containing cluster silver compounds

ABSTRACT

RECORDING MATERIAL SENSITIVE TO ELECTROMAGNETIC RADIATION AND OR HIGH ENERGY ELEMENTARY PARTICLES COMPRISING A SILVER-CONTAINING LAYER IN WHICH THE SILVER IS PRESENT AS A CLUSTER SILVER COMPOUND HAVING A PROPORTION OF THE SILVER ATOMS THEREOF ARRANGED IN A PLURALITY OF LAYERS OF MONOATOMIC THICKNESS WITH METAL-METAL BONDS EXISTING BETWEEN THE SILVER ATOMS OF ANY ONE LAYER, AND RECORDING PROCESS USING THE SAME. THE SILVER KETENIDE CONTAINING SILVER ATOMS ARRANGED IN MONO-ATOMIC LAYERS IS PREFERABLY PREPARED BY THE REACTION OF SILVER ACETATE AND ACETIC ANHYDRIDE IN PYRIDINE.

United States Patent 3,726,687 RECORDING MATERIAL CONTAINING CLUSTERSILVER COMPOUNDS Derek Bryce-Smith, Highland Wood House, Mill Lane,Kidmore End, County of Oxfordshire, England, and Ernest Thomson Blues,36 Reeds Ave., Earley, Reading, England No Drawing. Filed Sept. 21,1970, Ser. No. 74,156 Claims priority, application Great Britain, Sept.25, 1969, 47,325/69 Int. Cl. G03c 1/02 US. Cl. 96114.6 15 ClaimsABSTRACT OF THE DISCLOSURE Recording material sensitive toelectromagnetic radiation and or high energy elementary particlescomprising a silver-containing layer in which the silver is present as acluster silver compound having a proportion of the silver atoms thereofarranged in a plurality of layers of monoatomic thickness withmeta1-metal bonds existing between the silver atoms of any one layer;and recording process using the same. The silver ketenide containingsilver atoms arranged in mono-atomic layers is preferably prepared bythe reaction of silver acetate and acetic anhydride in pyridine.

This invention relates to photographic recording materials consisting ofor including a layer containing a silver compound, and particularlyrelates to photographic recording materials wherein the said silvercompound contains silver atoms arranged and associated in a mannerhereinafter referred to as cluster silver. The term compound used hereinand in the claims hereof in relation to cluster silver includes simplecompounds and complexes thereof with other compounds.

There has been an increasing interest in metal clus ter compounds inwhich the metal atoms thereof are arranged and associated with eachother in a way which is different from the arrangement in conventionalcompounds of such metals. Recent work (E. T. Blues and D. Bryce-Smith,Discuss Faraday Soc., 1969, 47) has shown that silver and silvercompounds having anomalous properties may be obtained, for instance byreacting silver salt with acetic anhydride, possibly in the presence ofa tertiary base, possibly followed by a heating step. It was suggestedthat such compounds (e.g. complexes) are consistent with a silverketenide structure Ag C O and furthermore that such compounds maycontain silver clusters (cluster silver) having metal-metal bonding,possibly involving sheets of silver atoms. Further work has confirmedthis hypothesis (E. T. Blues et al., Chem. Soc., Chemical Communications1970, 699-701) wherein silver ketenide prepared by the reaction ofsilver salts with ketene, or with acetic anhydride in the presence ofpyridine or triethylamine, is shown by X-ray and electron diffractionanalysis to have a structure wherein silver atoms are in mono-atomiclayers, the distance between silver atoms in a layer being 2.84 A., anda strong direct bond exists between the silver atoms. The inter-layerseparation may vary. Thus for silver ketenide the inter-layer distanceis 5.856 A., and for silver ketenide/pyridinate complex the inter-layerdistance is approximately twice this value. The layers are separated byketenide (C 0) groups.

Recent work has indicated that the cluster silver configuration incluster silver compounds comprises an arrangement of silver atoms inmono-atomic layers which is generally but not exclusively characterizedby at least a proportion of the silver atoms being separated from eachother, by a distance of less than 3.0 A.

Silver ketenide and silver ketenide complexes may be 3,726,687 PatentedApr. 10, 1973 converted to other silver compounds or complexes by ligandexchange, and in such other silver compounds or complexes at least aproportion of the silver atoms retain the cluster silver configurationof silver ketenide. Thus cluster silver halides may be produced by thereaction of silver ketenide complexes with a halide salt to provide aprecipitate of the cluster silver halide or complexes thereof. By thismeans cluster silver chloride, cluster silver bromide and cluster silveriodide may be obtained. Such cluster silver halide or complexes may owetheir anomalous properties to a residual proportion of silver ketenideassociated therewith.

The term cluster silver compounds used in the present specfication andclaims is hereby defined as silver compounds (which term includes simplecompounds or complexes thereof with other compounds) wherein at least aportion of the silver atoms are arranged in a plurality of layers ofmono-atomic thickness, and wherein metal-metal bonds exist between thesilver atoms of any one layer.

It has now been discovered that a useful photographic recording materialis provided by a recording element containing one or more cluster silvercompounds as hereinbefore defined. Preferably the cluster silvercompounds are applied in or to a sheet material e.g. in a binder layer.

Particular cluster silver compounds are silver ketenide, complexes ofsilver ketenide with certain tertiary bases as hereinafter described,complexes of silver ketenide or silver ketenide/ tertiary base with acomplexing compound e.g. a salt, for instance silver chloride, silverbromide or silver iodide, and cluster silver salts, e.g. cluster silverchloride, bromide and iodide.

The binder may be a hydrophilic binder, e.g. a watersoluble colloid ofthe type used in silver halide emulsion layers, preference being givento gelatin; or an organophilic binder i.e. a binder soluble in organicsolvents, for example polyvinylbutyral, which may be used in associationwith a hydrophilic binding agent e.g. acting a dispersing agent orprotective colloid. Useful in that respect are hydrophilic colloids thatare soluble in water and in a lower alkanol e.g. methanol. A suitablebinding agent combination contains polyvinylbutyral andpoly-N-vinylpyrrolidone. Organophilic binding agents may be applied fora solution in an organic solvent or as a dispersion from an aqueousmedium e. g. as a latex.

Suitable organophilic binding agents are known from electrophotographicrecording materials containing dispersed photoconductive pigments. Incases wherein the recording layer needs a particular good mechanicalstrength cross-linked binding agent structures may be formed. The layerof binder containing cluster silver compound(s) may be a self-supportinglayer or such a layer on a support.

The recording material according to the invention on exposure toelectromagnetic radiation, e.g. visible light or infrared radiation, orexposure to high-energy electromagnetic radiation, is capable of formingan image in the exposed areas. On exposure to appropriate radiation aprint-out image may be obtained, or a latent image which may bedeveloped. For example by using a compound having reducing properties ase.g. contained in a conventional photographic silver halide developer.

Cluster silver compounds for incorporation in the binder for useaccording to the invention may be produced by any of the methodsdescribed in United States patent application 21,539 or in the Chem.Soc. Chemcal Communications publication hereinbefore referred to.

Silver ketenide has the empirical formula Ag C O and is considered tohave a structural arrangement as set forth on page 700 of the ChemicalSociety Chemical Communications publication.

In particular such cluster silver complexes may be prepared bycontacting a compound of conventional silice ver with a carboxylic acidanhydride, the reactants be ing selected so that at least one of thereactants contains a CH C-- group, whereby a yellowish or yellowish-redprecipitate of complex is formed, and separating the said complex. Theseparated complex is preferably treated with an aqueous medium ormethanol, or by heating, or a combination of both, for such acombination of time and temperature that the complex develops a magneticsusceptibility which is field-dependent.

The particular silver compound and the particular organic anhydride usedare selected so that a yellowish or yellowish-red product is formed inthe reaction medium. Subject to the said test for suitability, specificclasses and specific examples of silver compounds which may be used toform the said yellowish or yellowish-red complexes containing clustersilver for use according to the invention include the following.

Silver salts of monocarboxylic acids, e.g. form-ate, acetate, trimethylacetate, trifluoroacetate, propionate, isobutyrate or lactate, orunsaturated acids e.g. acrylate; or aromatic acids, e.g. benzoate andphenylacetate.

Silver salts of polycarboxylic acids, e.g. oxalate, malonate, succinate,or adipate, or unsaturated acids, e.g. maleate or fumarate; or aromaticacids, e.g. phthalates.

Silver salts of sulphonic acids, e.g. methane sulphonate, benzenesulphonate or toluene p-sulphonate.

Miscellaneous organic salts, e.g. silver naphthenate andphenylacetylide.

Silver salts of inorganic acids, e.g., sulphate, nitrate, nitrite,carbonate, fluoride, perchlorate, tetrafluoroborate,hexafluorophosphate.

Miscellaneous inorganic compound, e.g. silver oxide or hydroxide.

Conventional silver metal may be used as a starting material in thepresence of a reagent that converts the silver to a silver compound ashereinbefore described, e.g. nitric acid or peracetic acid.

Certain conventional silver compounds may not in practice produce therequired yellowish or yellowish-red complex when reacted with an organicanhydride according to the invention, and their unsuitability may berecognised by their failure of the reaction medium to develop a yellowor reddish-yellow complex. Such compounds include silver halides (otherthan silver fluoride), silver pseudo halides and silver sulphide.

Anhydrides which may be used in the said preparation to produce theyellowish or yellowish-red complex include anhydrides of monocarboxylicacids, e.g. acetic anhydride, propionic anhydride, n-butyric anhydride,nvaleric anhydride, iso-valeric anhydride, caproic anhydride, caprylicanhydride and lauric anhydride. Anhydrides of an unsaturatedmonocarboxylic acid may be used, e.g. acrylic anhydride. Mixedanhydrides of organic acids or organic and inorganic acids may be used,for instance acetic-isovaleric anhydride, acetic butyric anhydride,acetyl chloride, and acetyl fluoride.

In carrying out the initial reaction to form the yellow or yellowish-redcomplex, it is necessary that the said -CH OO- group be present in atleast one of the reagents. For example the said CH -CO-- group may bepresent as the acetate group in silver acetate starting material, or maybe present in the organic anhydride. Thus suitable combinations ofreactants are silver acetate and benzoic anhydride or silver benzoateand acetic anhydride. Such combinations as silver benzoate and benzoicanhydride may not however be used, as such a combination does notinclude a CH CO-- group.

In the reaction to produce the said yellow or yellowishred silvercomplex, carboxylic acid(s) are formed from the starting materials. Forinstance with silver acetate and acetic anhydride, acetic acid is themajor by-product, and as such tends to inhibit the formation of the saidcomplex and should therefore preferably be removed during the course ofthe reaction, for instance by fracof a large molar excess of theanhydride component based on the silver reactant, e.g. from 20:1 to40:1, whereby the carboxylic acid is diluted and its inhibitory effectdecreased.

The reaction may be carried out under air or an inert atmosphere forexample argon. Nitrogen is not an inert gas, as nitrogen may enter theproduct.

The reaction between the silver compound and the organic anhydride mayif required, be effected at an elevated temperature between C. and theboiling point of the reactants, prefer-ably above C., and particularlyby refluxing the reaction medium.

An alternative procedure for effecting the reaction, which is apreferred method, permits the reaction to be effected rapidly and withgood yields at room temperature. Said preferred method compriseseffecting said reaction between the silver compound and the organicanhydride in the presence of at least one tertiary amine.

Specific examples of tertiary amines which may be used in the saidpreferred method include quinoline, isoquinoline, N,N-dimethyl aniline,2,3-dimethyl quinoline, 2,6- dimethyl quinoline,N,N-dimethyl-o-toluidine, N-methyl pyrrolidine, Z-methyl quinoline,S-methyl quinoline, apicoline, B-picoline, v-picoline, pyridine,quinoline, trimethylamine, triethylamine, triisobutylamine,N-methylpiperdine, N-methylmorpholine and diazabicyclooctane.

Certain very weak tertiary bases, for example triphenylamine, may nothowever exert a significant effect on the reaction rate, and theselection of suitable tertiary amines may readily be determined byexperiment. A useful tertiary amine is a trialkylamine, e.g.trimethylamine or triethylamine. Silver ketenide derived from ketene andsilver acetate or from acetic anhydride and silver acetate, in thepresence of triethylamine, has particularly light-sensitive properties.Particularly useful complexes are those of silver ketenide with eithersilver chloride or silver bromide. If silver ketenide is contacted witha solution of silver chloride or silver bromide in concentrated ammoniaat room temperature, mixed complexes of halide and ketenide are obtainedwhich are particularly sensitive. Thus the sliver bromide complexes aresensitive to visible and infra-red light.

A particularly preferred method of forming silver ketenide comprisesreacting silver acetate and acetic anhydride in the presence ofpyridine. One variant of the said method is to suspend the silveracetate in the silver anhydride and to add pyridine drop-wise to thesuspension at room temperature (20 C.) whilst stirring. By

this means a pyridinate complex is formed. Silver kete nide may beobtained from the pyridinate by heating, preferably with aceticanhydride, whereby pyridine is removed. Alternatively, products for useaccording to the present invention may be obtained by contacting thepyridinate with a hydroxyl group containing compound, e.g. methanol orwater.

Silver ketenide has absorption maxima at about 445 and 468 nm. and showslight sensitivity at these wavelengths.

However simultaneous exposure to shorter wavelength radiation maydecrease sensitivity, i.e. blue and UV- radiation either may inhibit orreverse the darkening process.

The photosensitive compounds used in recording materials and processesaccording to the present invention may be spectrally sensitized withcompounds and according to recording techniques known to those skilledin the art of preparing silver halide photographic materials.

The presence of silver ketenide in materials obtained by the variousmethods as hereinbefore described may be tional distillation, or itseflect minimized by the presence tested by exposing the material e.g.suspended on glass wool, with hydrogen chloride gas diluted withnitrogen to prevent detonation of the complex. Ketene gas is firstproduced, followed by acetyl chloride.

The following examples of the invention are provided.

Example 1 A silver iodide/silver ketenide complex was prepared in afirst stage by heating under reflux under argon in the dark a mixture ofsilver acetate with an excess of acetic anhydride. In a second stage 2-1g. of the obtained silver ketenide product were heated with 23 g. ofmethyl iodide, in 200 ml. of n-hexane for six weeks in the dark. Theresulting yellow product was filtered, washed with pentane and dried.Yield: 29.5 g. of silver iodide/silver ketenide complex.

4 g. of the complex thus obtained were dispersed in a liquid mixture of70 g. of a by weight solution in methanol of polyvinylbutyral (averagemolecular weight 38,000--45,000 containing 80% of acetal groups) and 10g. of a 10% by weight solution of poly-N-vinylpyrrolidone (averagemolecular weight 40,000) in methanol. The dispersion thus obtained wasdiluted with '52 ml. of methanol and thereafter applied to aphotographic paper at such a loading that the formed layer containedsaid complex in an amount corresponding with 33 g. of silver per sq. m.of paper, and the layer dried.

The thus obtained photosensitive recording material was exposed for 185sec. through a line image. The recording layer received 109,000 luxemitted by tungsten incandescent lamps in correspondence with theoptically clear image parts of the original. A print-out image wasobtained having a maximum optical density of 0.64 measured inreflection. The minimum density was 0.1-8.

The procedure was repeated using conventional silver iodide or silverbromide instead of the silver iodide/ silver ketenide complex, thesilver iodide and silver bromide being used in corresponding amounts,and the following optical density values were respectively obtained.

urex. miu.

.AgI 0. 10 0. 10

AgBr O. 20 0. 10

EXAMP-LE 2 20 g. of silver acetate was dissolved in 80 ml. of pyridine,and 200 ml. of acetic anhydride slowly added at 20 C. with stirring. Onstanding for 10 minutes a yellow precipitate had formed.

The yellow precipitate Was filtered otf and washed with aceticanhydride, and the solid thus obtained introduced into a 500 ml. flaskwith 150 ml. of acetic anhydride. The mixture was then slowly heateduntil all the pyridine was driven oif and only acetic anhydride wasbeing distilled over. The product complex was then filtered ofi, washedwith methanol, and a slurry formed with acetone, and the slurry washedwith methanol and ether being filtered after each washing.

The dried yellow product analyzed as Ag C O, and consisted of silverketenide, the silver atoms of which were arranged in monoatomic sheets,as shown by X-ray analysis.

The magnetic susceptibility of the silver ketenide was measured indifferent magnetic fields at 22 C., using a Gouy balance, and was foundto be weakly field dependent.

'2 g. of the said complex were added to 20 ml. of water and dispersed in80 ml. of a 10% by weight aqueous solution of gelatin.

The obtained dispersion was coated at a loading of 1 g. of complex persq.m. onto a baryta coated photographic paper base. The thus obtainedlayer was dried at 30 C. and had a yellow appearance.

The dried recording layer was contact-exposed for 2 min. with normaldaylight using a step wedge having a constant 0.2 as original.

The exposed recording layer was developed at 20 C. in a developingliquid having the following composition:

G. p-Methylaminophenol sulphate 1.5 Hydroquinone 6 Anhydrous sodiumsulphite 50 Anhydrous sodium carbonate 32 Potassium bromide 2 Water to1000 ml.

The developed wedge image representing 15 reproduced steps was fixed ina fixing liquid having the following composition:

G. Sodium thiosulphate 200 Anhydrous sodium sulphite 12 Potassiumdisulphite (-K 'S O 12 Water to 1000 ml.

After 30 min. rinsing and drying a stable wedge print of black silver ona white image background was obtained.

We claim:

1. A recording material sensitive to electromagnetic radiation and/orhigh energy elementary particles comprising a layer of a binder mediumcontaining a cluster silver compound which is yellow to reddish yellowin color and comprises silver ketenide, a complex of silver ketenidewith a tertiary base, a complex of silver ketenide with silver chloride,silver bromide, silver iodide or mixture thereof or a complex of silverketenide with a tertiary base and with silver chloride, silver bromide,silver iodide or mixtures thereof, said cluster silver compound beingcharacterized in that at least a portion of the silver atoms arearranged in a plurality of layers of mono-atomic thickness with directmetal-metal bonds between the silver atoms of a given layer, thedistance between any silver atom in such layer and the nearest silveratom being generally less than about 3 A.

2. A recording material according to claim 1, wherein said layercontains a hydrophilic binding agent.

3. A recording material according to claim 2, wherein the hydrophilicbinder is a water-soluble colloid.

4. A recording material according to claim 3, wherein the hydrophilicbinder is gelatin.

5. A recording material according to claim 1, wherein said layercontains an organophilic binding agent.

6. A recording material according to claim 1, comprising a supportcarrying said layer.

'7. A recording material according to claim 1, wherein said clustersilver compound is obtained by reacting a silver salt with a carboxylicacid anhydride, at least one of the reactants being selected to containa CH CO group, whereby a yellowish or yellowish-red complex isprecipitated, and separating the said complex.

8. A recording material according to claim 7, wherein said separatedcomplex is contacted with a hydroxyl group containing compound.

9. A recording material according to claim 7, wherein the carboxylicacid anhydride is acetic anhydride.

10. A recording material according to claim 7, wherein the said reactionis carried out in the presence of a tertiary amine.

11. A recording material according to claim 10, wherein the saidtertiary amine is a trialkylamine.

12. A recording material according to claim 10, wherein the saidtertiary amine is pyridine.

13. A recording material according to claim 7, wherein the said reactionis carried out in the presence of silver chloride, bromide or iodide, ora mixture thereof.

14. A recording method which comprises image-wise exposing a layercomprising in a binder medium a cluster silver compound which is yellowto reddish yellow in color and comprises silver ketenide, a complex ofsilver ketenide with a tertiary base, a complex of silver ketenide withsilver chloride, silver bromide, silver iodide or mixtures thereof or acomplex of silver ketenide with a tertiary base and with silverchloride, silver bromide, silver iodide or mixtures thereof, saidcluster silver compound being characterized in that at least a portionof the silver atoms are arranged in a plurality of layers of monoatomicthickness with direct metal-metal bonds between the silver atoms of agiven layer, the distance between any silver atom in such layer and thenearest silver atom being generally less than about 3 A., toelectromagnetic radiation and/or high energy elementary particlesresulting in the formation of a. recorded image in said layer.

15. A recording method according to claim 14, wherein the image isdeveloped by means of a reducing compound.

References Cited UNITED STATES PATENTS J. TRAVIS BROWN, Primary ExaminerI. R. HIGHTO-WER, Assistant Examiner US. Cl. X.R. 9667

